Wireless energy transmission refers to technologies that transmit electrical energy from a power source to a separate device, such as a cell phone or laptop computer without cables or conductors. Two architectures that are widely used for wireless power transfer are antennas (i.e., antenna-based near-field resonator) and inductive coupling. Antenna-based resonant systems offer better efficiency and greater power transfer distances than inductive coupling based technologies. The antenna coil typically has a narrow operating range in terms of drive voltage, typically 5-40V depending on the power level and coil design.
Wireless power transmitters typically drive the antenna with a two stage power converter. The first stage rectifies the AC mains to an intermediate low voltage DC bus (5-40V). The second stage is an inverter that converts the intermediate low voltage DC bus voltage to AC that excites the antenna coil. These power conversion architectures are complex, costly and inefficient.